Pulse-generator circuits that permit independent control of pulse widths and the delays between successive pulses. In several embodiments, a pulse-generator subcircuit includes a transmission-line segment comprising first and second conductors, configured such that the first conductor is coupled to a first DC potential. The pulse-generator subcircuit further includes a terminating resistor coupled to a first end of the second conductor of the first transmission-line segment; this terminating resistor is matched to the characteristic impedance of the transmission-line segment. The pulse-generator subcircuit further includes first and second switches, controlled by first and second timing signals, respectively, and configured to selectively and independently connect respective first and second ends of the first conductor to a second DC potential. This second potential may be ground, in some embodiments, while the DC potential supplied to the pulse-generator subcircuit by the power-supply subcircuit may range from a very small voltage to voltages exceeding a kilovolt.